Stability analyses of inclined rotor bearing system based on non-linear oil film force models

Stability characteristics of inclined rotor bearing system are investigated by numerical and experimental research. The dynamic equation is established based on finite element method. To describe the oil film force of journal bearing, Capone's short bearing model and a variational approximate finite bearing model are employed separately and compared. Different inclination states are considered as different radial loads on journal bearing. Newmark method employed to solve the dynamic equation and stability characteristics are discussed. The numerical results show that the short and finite bearing models have differences on describing the oil force induced oil whirl and whip. Compared with the short bearing model results, unstable zones given by finite bearing model have larger breadth and larger whirl/whip amplitude. With the development of rotor inclination, the unstable threshold decreases and the unstable zone become wider. Influences of parameters on unstable thresholds are also affected by rotor inclination. Comparisons of numerical and experimental results show that the finite bearing model results are more close to the test results.